Method of manufacturing laminated transparent panels incorporating an array of crimped heating wires



Aug. 4, 1970 J, E PQWELL ETAL I 3,522,651

METHOD OF MANUFACTURING LAMINATED TRANSPARENT PANELS INCORPORATING ANARRAY 0F CRIMPEI) HEATING WIRES driginal Filed May 5} 1965 9Sheets-Sheet 2 Aug. 4, 1970- J. E. POWELL ETAL 3,522,651 METHOD OFMANUFACTURING LAMINATED TRANSPARENT PANELS INCORYORATING AN ARRAY OFCRIMPED HEATING WIRES Original Filed May 5, 1965 9 Sheets-$119 3 Aug. 4,1970 J POWELL ETAL 3,522,651

METHOD OF MANUFACTURING LAMINATED TRANSPARENT PANELS INCORPORATING ANARRAY 0F CRIMPED HEATING WIRES 9 Sheets-Sheet 4.

Original Filed Bay 5, 1965 Aug. 4, 1970 POWELL, ETAL 3,522,6S1

METHOD OF MANUFACTURING LAMINATE TRANSPARENT PANELS INCORPORATING ANARRAY OF CRIMPED HEATING WIRES 9 Sheets-Sheet 5 Qriginal Filqd May 5,1965 W 5 4 QWM {111i F 1. W V/ B H u m 8 U p m M 1 8 u Aug; 4, 1970POWELL ETAL 3,522,651 METHOD OF MANUFACTURING LAMINATED TRANSPARENTPANELS mconronmme AN ARRAY 0F cnmran HEATING wmns Original Filed May 5.1965 9 Sheets-Sheet 6 Aug. 4, 1970 J. E. POWELL ETAL 3,522,651

METH0D10F MANUFACTURING LAMINATED TRANSPARENT ?ANELS INCQRPORATING ANARRAY 0F CRIMPED HEATING WIRES 9 Sh t -Sh t Original Filed May 5, 196589 s as 7 J. E. POWELL L 3,522,651 FACTURING LAMINATED TRANSPARENTPANELS INCORPORATING AN ARRAY OF CRIMPED HEATING WIRES 9 Sheets-Sheet 8U M M "w W w w aw H v. T 3 0 u M 7 M 9 u 1 F l 4 a m. m u .m A r 0 Aug.4, 1970 METHOD OF MANUFACTURING LAMINATED TRANSPARENT PANELSINCORPORATIHG AN ARRAY 0F CRIMPED HEATING WIRES 9 Sheets-Sheet 9Original Filed Bay 5, 1965 FIG. 14.

FIG. 13.

' US. Cl. 29611 United States Patent 01 iice 3,522,651 Patented Aug. 4,1970 3,522,651 METHOD OF MANUFACTURING LAMINATED TRANSPARENT PANELSINCORPORATING AN ARRAY OF CRIMPED HEATING WIRES John Ernest Powell,Birmingham, and Malcolm Walter Lacey, Tipton, England, assignors tTriplex Safety Glass Company Limited, London, England, a British companyOriginal application May 5, 1965, Ser. No. 453,433. Divided and thisapplication Mar. 18, 1969, Ser. No. 825,477. 0 Claims priority,application Great Britain, May 5, 1964, 18,599/64; Jan. 28, 1965, 3,728/65 Int. Cl. H05b 3/00 2 Claims ABSTRACT OF THE DISCLOSURE A method ofcrimping arrays of heating wires prior to their incorporation intransparent panels, such as the backlights of automobiles, so that lightdiffraction is reduced. The method comprising the steps of passing thearray between a pair of rotating ribbed rollers which mesh with eachother, so that each wire is formed with undulations, and then pressingthe ends of the wires against a sheet of transparent material which isto form part of a laminated panel, so that they rotate in random mannerand the undulations lie in the same plane as the sheet, then scouringthe wires to the sheet.

This is a division of application Ser. No. 453,433 filed May '5, 1965.

The invention relates to transparent panels incorporating arrays ofheating wires such that in use, when the wires are connected to asuitable source of electricity, the current passing through the wiresheats the wires and the panel. Panels of this kind are referred to inthis specification as wired panels. Wired panels may be used for manypurposes, and may, for example, be used as the windscreens andbacklights of motor vehicles. The invention is particularly concernedwith the method of crimping the arrays and inserting them in a laminatedanel. p The wires incorporated in wired panels are relatively thin, andthis invention is only concerned with arrays of heating wires of whichthe individual wires are less than 0.003 inch in diameter. The wires maybe made of a nickel and chromium alloy or of cupro-nickel, but the wiresare preferably made of tungsten. Tungsten wire is particularly suitableas it is less reflective than the other types of wire mentioned, it hasa higher specific conductivity so that the heating efiect obtained withtungsten wire is equivalent to that obtained with another wire ofgreater thickness, and it is available commercially in a thickness assmall as 0.0005 inch. The handling of such thin wire is difficult, andit will be appreciated that the formation of an array of long, straightwires in closely spaced parallel relationship, for incorporation in awired panel, gives rise to numerous difficulties. In one method employedhitherto for forming such an array, wire has been unwound by hand from aspool and arranged on a frame comprising two parallel rows of pegs, thewire being passed round a peg in one row, passed across to the other rowand round a peg in this row before being passed back again to the firstrow where it is passed round the peg adjacent to the first peg. Theprocess is continued, the wire passing round successive pegs in eachrow, and an array of parallel wires is built up between the rows. Thismethod is slow and can only be carried out by a skilled person. Inanother method which has also been employed hitherto a plurality ofwires has been drawn simultaneously from a plurality of spools through acomb-like guide so as to form a band of closely spaced parallel wires.Successive bands are disposed side-by-side to form an array. This methodsuffers from the disadvantage that in practice it is found that wires ofthe same nominal diameter but from different spools vary somewhat inactual diameter. Although these variations are within normalmanufacturing tolerances they have an adverse effect on the wired panelin which the wires are incorporated, for in use the ratio of the heatgenerated in one wire to that generated in another is proportional tothe ratio of the square of the diameter of the one wire to the square ofthe diameter of the other.

When arrays of wires of the kind set forth are incorporated in atransparent panel, such as the backlight of a vehicle, there issometimes a problem caused by light diffraction from the wires and thisproblem is reduced by crimping the wires before their incorporation inthe transparent panel.

The object of the present invention is to overcome or reduce thesedifliculties by providing an improved method of crimping the wires andincorporating them in a laminated panel of the kind set forth.

According to one aspect of the present invention there is provided amethod of crimping wires of less than 0.003 inch diameter forming anarray of heating wires suitable for incorporation in a laminatedtransparent panel, the array having supporting edge members attachedthereto to maintain a spaced disposition of the wires whilst beingcrimped, which method comprises attaching one supporting edge member ina reciprocating device and drawing the array of wires between a pair ofrotating ribbed rollers in one direction, the rollers meshing with eachother so that each wire of the array is formed with undulationssimultaneously, the undulations projecting from the main plane of thearray.

According to another aspect of the invention there is provided a methodof manufacturing laminated transparent panels incorporating an array ofheating wires, comprising the steps of first crimping the wires formingthe array so that each wire is formed with undulations which projectfrom the main plane of the array, laying the array of crimped wiresagainst one side of a first sheet of transparent material which is toform part of a laminated panel, crimped end portions of the wires thenbeing pressed against said first sheet so that the wires rotate inrandom manner and the undulations lie in the plain of the array, thensecuring the wires to the first sheet prior to a second sheet formingthe other part of the laminated panel being joined to the first sheet.

Prior to crimping, the arrays of wires are wound onto a frame whichforms part of the winding, apparatus described herein and shown in FIGS.1 to 6 of the accompanying drawings but which forms the subject matterof the claims filed with our co-pending U.S.A. application Ser. No.453,433 filed on May 5, 1965.

The frame is preferably so shaped as to present two or more spaced,parallel corner members around which each turn of wire passes, eachcorner member being so shaped that the wire forms a smooth curve whereextending around it. There may be two corner members or more, aparticularly convenient form of frame having four corner members soarranged that each turn of Wire is substantially square. Preferably anarray of wires is formed from those parts of the turns extending betweeneach successive pair of corner members, the number of arrays thus beingequal to the number of corner members. In this case a support ispreferably introduced on each side of each corner member, immediatelyadjacent to the member. The supports may be present before the wire iswound onto the frame or may be introduced subsequently.

The invention will be more particularly described with reference to theaccompanying drawings, in which:

FIG. 1 is an end elevation of a winding machine for use in making arraysof wires,

FIG. 2 is a plan view of the machine shown in FIG. 1,

FIG. 3 is a side view, to a larger scale, and partly in section, of partof the winding machine shown in FIGS. 1 and 2,

FIG. 4 shows a sub-frame for use on the winding machine shown in FIGS. 1to 3,

FIG. 5 is a front view, to a larger scale, of a clamp on the windingmachine and a corner of a sub-frame held by it,

FIG. 6 is a section substantially along the line 6-6 of FIG. 5,

FIG. 7 is a side view of a crimping machine for use in crimping thewires in an array, one side having been removed to reveal the interior,

FIG. 8 is a front view of the guide for the carrier which forms part ofthe crimping machine shown in FIG. 7,

FIG. 9 is a view, to a larger scale, of the central part of the guideshown in FIG. 8, and assOciated parts, some of which are shown insection,

FIG. 10 is a section, to a larger scale, along the line 10-10 of FIG. 9,

FIG. 11 shows a portion of one of the ribbed crimping rollers, to aconsiderably larger scale, this figure merely serving to illustrate theshape of the ribs,

FIG. 12 is a diagrammatic view illustrating a later process in themanufacture of a wired panel,

FIG. 13 shows a completed wired panel,

FIG. 14 shows a corner of the panel shown in FIG. 13 but to a largerscale, and

FIG. 15 shows this corner in perspective with parts broken away toreveal the construction.

The machine shown in FIGS. 1 to 3 comprises a stand formed with a recess21, and having a pair of upstanding aligned bearings 22, one at eitherend of the recess. A frame is mounted between the bearings for rotationabout a horizontal axis. The frame includes a pair of spaced, parallelspiders 23 each spider having four arms 24 projecting radially outwardsfrom one end of a short spindle 25, the arms being at 90 intervalsaround the axis of the spindle. The spindles 25 of the spiders 23 areco-axial and directed away from each other, the spindles being rotatablymounted in bearings 22. Each arm 24 of one spider 23 is connected to acorresponding arm of the other spider by a bar or bars 26 parallel withthe axis of the spindles 25 and spaced a little way from it. Ascrew-threaded rod 27 extends along one side of each arm and issupported by bearings 28, near each end, for rotation about its ownaxis, which axis is normal to the axis of the spindles 25. Each rod 27carries a bevel gear 29 at its inner end which meshes with a bevel gear30 mounted on a shaft 31 coaxial with the spindles 25 and extendingbetween them. The ends of the shaft 31 are rotatably mounted in thespindles 25, which are hollow, and one end carries an extension 32 whichprojects from the outer end of one spindle 25 and can be releasablyconnected to a hand-wheel 33 which is mounted on a spindle 34 rotatablein a bracket 35 and can be moved axially towards and away from the frameso that the extension 32, which is of square cross-section, can engageor disengage a correspondingly shaped recess in the spindle 34,

It will be seen that there are two bevel gears 30 on the shaft 31, onemeshing with the four bevel gears 29 on the rods 27 of one spider 23,and the other meshing with the four bevel gears 29 on the rods 27 of theother spider 23. Each screw-threaded rod 27 carries a non-rotating nut36 which is connected to one end of a corner bar 37. There are fourcorner bars 37, each in the form of a nonrotatable metal tube with asmooth outer surface, each corner bar being parallel with the axis ofthe spindles 25 and of the shaft 31 and extending between the nut 36 onthe rod 27 of one arm 24 on one spider 23, and the nut 36 on the rod 27of the corresponding arm 27 on the other spider 23. The four corner bars37 are equidistant from the axis of the spindles 25, but the distancecan be varied by rotating the shaft 31 relatively to the spindles 25 andspiders 23 which the aid of the handwheel 33.

A clamp is fixed to each end of each of the corner bars 37. The clampsare not shown in FIGS. 1 to 3, but one is shown in detail in FIGS. 5 and6. A two-armed bracket 40 is secured to the corner bar 37, the arms ofthe bracket projecting at right-angles to each other, and each pointingtowards an adjacent corner bar. Each arm carries an outwardly directedlocating pin 41 adjacent to its outer end, and also carries a subsidiarybracket 42 which is mounted on the outer face of the arm between the pin41 and the corner bar 37. The subsidiary bracket 42 has a clampingmember 43 pivotally connected to it. The clamping member 43 and thesubsidiary bracket 42 are both formed with pierced lugs 44 to whichhelical tension springs 45 are connected, the arrangement being suchthat the clamping member 43 can move over-dead-centre between theposition illustrated, in which a portion 46 with a forked end engagesthe pin 41, and a position in which the portion 46 is spaced away fromthe pin 41 and away from the arm of the bracket 40 on which the pin ismounted. The clamping member 43 includes an integral handle 46 enablingthe clamping member to be readily moved from one position to the other.

Supports 47, in the form of flat metal bars with slotted ends, can bemounted on the winding frame by means of the clamps. Two such supportsare shown in FIG. 4, and the end of one support is also shown in FIGS. 5and 6. In use the supports are mounted on the locating pins 41 andreleasably held in place by the spring-urged clamping members 43. Eachsupport conveniently forms part of a sub-frame, and is provided with acranked bracket 48 at each end. Each bracket is provided with a belt 49and wing-50 whereby it can be attached to one end of one side member 51of the sub-frame, as shown in FIG. 4, the ends of the side members 51being slotted. When the positions of the corner bars 37 are adjusted, asdescribed above, the distance between the pair of supports in eachsub-frame alters. In order to accommodate these alterations each sidemember 51 is provided at one end with a relatively extensive slot 52.Sets of side members of different lengths would usually be provided toextend further the range of possible adjustment.

A pulley 53 is fixed to that spindle 25 adjacent to the hand-wheel 33,and carries a driving band 54 which also passes over a pulley 55 drivenby an electric motor through change-speed gearing indicated generally at56. The mechanism is not described in detail as it is similar to that ofa lathe, the pulley 55 being in the equivalent position to the chuck ofa lathe. A screw-threaded shaft 57 below the pulley 55 is also driventhrough changespeed gearing by the same motor, and corresponds to thefeed screw of the lathe. A carriage 58 mounted on the equivalent of thesaddle of the lathe can thus be moved in a direction parallel with theaxis of rotation of the frame accurately synchronised with therotational movement of the frame.

In use a spool of wire (not shown) is mounted on the carriage 58, andthe wire is passed over grooved guide wheels 59 mounted on arms on thecarriage. Four subframes of the kind shown in FIG. 4 are mounted on theframe, and the end of the wire is attached to one of the supports 47 ofone of the sub-frames. The machine is then put in motion, and the framerotates in the direction indicated by the arrow A in FIG. 1. Wire isdrawn from the spool and forms a plurality of closely spaced turns asindicated by the dotted lines 60 in FIG. 1. The corner bars 37 andsupports 47 are so positioned that in use when a turn of wire is woundonto the frame it extends round each corner bar and touches the flatsurfaces of the two supports adjacent to it, and extends unsupportedbetween each support and the adjacent support close to the next cornerbar.

A wire feed device may be provided to control the wire as it unwindsfrom a spool. The rotation of the frame draws the wire through the wirefeed from the spool. The wire feed is so designed as to reduce thepossibility of wire breakage as far as possible. When relatively thickwire is used it may be possible to employ a wire feed similar to that ina sewing-machine and in which resistance is afforded by a pair ofspring-loaded plates or pads urged towards each other, the wire passingbetween them. When relatively thin wire is used, however, for exampletungsten wire 0.0005 inch thick, it is preferred to use a wire feed ofthe kind including the features which are described in British Pats.Nos. 572,003, 591,892 and 720,- 977. Whatever form of wire feed is usedthe arrangement is preferably such that the changes in rate of wire feedare kept as low as possible. It will be appreciated that when a frame ofthe kind illustrated is rotated at a uniform speed the rate of wire feedchanges somewhat, though the variation is less than it would be with aframe having two guides only. If the tension of the wire varies as thewire is being wound onto the frame there may be a tendency for someturns to sag. With a view to overcoming this tendency the corner bars 37and the supports 47 are preferably made smooth so as to enable any looseturns to be pulled tight as soon as the tension increases again. Thismay be unnecessary, however, if the wire tension can be maintainedsufiiciently even.

When the wire has been wound onto the frame it is secured to thesupports 47. The wire is preferably secured with the aid of an adhesivebut mechanical clamps may be used if desired. A clamp may, for example,comprise two parallel bars faced with resilient material. In thepreferred method a length of flexible, adhesive tape, is laid over theturns of wire on each support so that the wire and those parts of thesupport between successive turns of the wire adhere to the tape. Whenthis has been done the wire is severed, as with a razor blade, betweeneach corner bar 37 and one of the adjacent supports 47. It is found thatthe loose ends of wire extending from the other adjacent support curl upagainst the support and need not be cut off. After severing the wire theclamps are released and the sub-frames removed from the frame. {Even ifthere are no side members interconnecting the supports and forming withthem a rigid sub-frame the array of wires can quite readily be handledwithout damage; one support can be carried horizontally and the other,hanging below, then holds the wires taut. Alternatively the supports canbe held parallel with each other one in each hand, a moderate tensionbeing applied in order to prevent the wires becoming slack and tanglingwith one another. When the wire is wound onto the frame in such a mannerthat there is no significant slack in any turns which must be taken upafter the Wire is laid, the supports 47 and/or the corner bars 37 may besuch as to cause the wire to adhere to them. In a convenient arrangementa length of flexible tape with both surfaces adhesive is caused toadhere to a support or corner bar, as the case may be, before the wireis wound onto the frame. A new length of tape would normally be usedeach time wire is wound onto the frame. Any wire thus caused to adhereto a corner bar would be severed between the corner bar and both of theadjacent supports, the wasted ends formed in this way being removed whenthe adhesive tape is stripped from the corner bar.

In order to avoid any disturbance of the wire as it is being wound ontothe frame the whole winding machine is preferably enclosed in adraught-proof cabinet, which is conveniently provided with glass wallsso that the winding operation can be readily observed. The doors of thecabinet are closed in use. The operation of the machine may becontrolled by any suitable switching arrangement, and means may beprovided to enable the machine to switch itself off when arrays of apredetermined length have been formed. In order to avoid a jerk when therotation starts, such as might break the wire, the drive to the pulley55 is by way of a magnetic clutch 61; and a choke is introduced into thecircuit of the driving motor for a predetermined time in order to causethe frame to accelerate only gradually. Movement of the frame is alsocontrolled by a magnetic brake 62 which is gradually released asrotation starts.

The completed array of wires, extending between two supports, may belaid directly onto a sheet of glass which will form one side of alaminated panel. The array may then be secured in position by beingsprayed with a material which sets to form a thin transparent skin overthe glass and the wires. This material may be a solution in a volatilesolvent of the same material as is used for the interlayer of the panel.For example, the material may be a solution of polyvinyl-butyl aldehydein chloroform. When the array is secured in position the wires may becut, as with a razor blade, at the edges of the glass, whereupon thesupports can be removed, stripped of the ends of wires and replaced onthe frame.

The completion of the laminated panel may then proceed as follows:Bus-bars or feed conductors would normally be provided to join the wiresin parallel with one another, and these may be of any suitable form. Ina convenient construction the laminated panel may incorporate feedconductors of the kind described in our British Pat. No. 972,453.

When a panel made by the method described above, is in use it is foundthat on occasion light is reflected simultaneously from a group ofneighbouring wires so as to give the appearance of a shiny band in thepanel. Further, the array may act as a diffraction grating and give riseto the appearance of chromatic fringes. With a view to overcoming thisdifficulty the wire is crimped before it is incorporated in the panel.The crimping may be of any form provided that it renders the wire nolonger straight A machine for crimping the array of wires after thesupports have been removed from the frame is illustrated in FIGS. 7 to11. The machine is housed in a glass panelled cabinet '65 the doors ofwhich are closed in use. The machine includes a guide, shown separatelyin FIG. 8, mounted at an angle of about 20 to the vertical. The guidecomprises a framework 66, made from angle-secfion members, and hasmounted on its front, upwardly-facing side a plurality of rollers 67freely rotatable about axes normal to the main plane of the framework66. A carrier having parallel side members 68 and transverse members 69is mounted on the front face of the framework, the side members runningbetween pairs of rollers 67. The carrier is connected to a chain 70which extends over a sprocket wheel 71 at the top of the cabinet and isconnected to a counter-weight (not shown). Racks 72 are secured to theunderside of the side members 68 and engage pinions 73 fixed on a shaft74 mounted in bearings 75 on the framework 66. The shaft 74 also carriesa pulley 76 which is connected by a belt to an electric motor 77. Aribbed roller 78 is mounted between bearings 79 on the framework 66, ashort way below, and rather in front of the shaft '74. The roller has anextension at one and carrying a pulley 80 also driven by a band from themotor 77. A similar roller 81 is mounted in bearings 82 on arms 83forming part of a swinging frame pivoted to the framework 66 at 84. Asshown in FIG. 10 the ribbed rollers 78 and 81 can mesh with each other,so that when roller 78 is driven the roller 81 also rotates. Anadjustable stop 85 prevents the two rollers meshing with each other tootightly and maintains them sufficiently far apart to enable an array ofwires to extend between them without being crushed. The swinging framecan be moved to the position shown in FIG. 7 by means of a pneumaticpiston-andcylinder unit 86 pivotally connected to the cabinet 65 and tothe swinging frame.

In use the array of wires with its supports is mounted on the carrier,the rollers 78 and 81 are brought together, the motor 77 is started, andthe carrier moves upwards, carrying the array with it, whilst therollers rotate. The meshing ribs on the rollers crimp the wires, and toavoid any undue strain the rate or movement of the carrier is equal tothe peripheral speed of the rollers. The movement of the parts of themachine are conveninently controlled by micro-switches, such as theswitches 87 shown in FIG. 9 and 10.

The machine is preferably automatic so that once started the frontroller 81 is brought into engagement with the rear roller 78, the rearroller is driven and the carrier raised, the front roller 81 is swungforwards and upwards, and the carrier is lowered to its originalposition.

The shape of the ribs on the rollers is illustrated in FIG. 11, and itis found that in spite of the angular shape of the ribs the wire formsundulations similar to those of the sine curve. During crimping, theeffective legnth of the wires is reduced, so it is necessary to mountthe supports on the holder in such a manner that they are free to movetowards each other somewhat. The upper support, indicated by dottedlines 64 in FIG. 9 and shown in full in FIG. 10, is mounted on pins 88which engage the slots 7 in the ends of the support, and is locatedagainst endwise movement by studs 89. The lower support rests on atransverse member 90 at the lower end of the holder. If the supports areinterconnected by side members 51 the wing nuts 50 at their lower endsare slackened so as to allow the associated bolts 49 to slide up theslots 52. The arrangement is such that when an array of wires has beencrimped and the front roller 81 has been swung forwards and upwards thewires lift themselves away from the rear roller 78 sutficiently far toenable the array to be lowered without the crimped wires fouling theroller 78.

Typical arrays in accordance with the present invention, made fromtungsten Wire 0.0005 inch in diameter, may be up to inches wide, withwires from 10 inches to inches long at spacings of between 8 and 14 tothe inch. When the wires are crimped the pitch (i.e. the distance fromcrest to crest may be about 0.08 inch and the amplitude about 0.008inch. These figures are given as examples only and are not to beconsidered as limitative.

After the array of wires has been crimped it is removed, with thesupports, from the crimping machine. It is then incorporated in a wiredpanel in any suitable manner, such as that described in our British Pat.No. 972,453 mentioned above. Unless special precautions are taken,however, the plane of the undulations in each wire will initially beroughly at rightangles to the plane of the surface of the glass, and theundulations may be pressed out of the wires, at least to some extent,when the interlayer is applied to the sheet. To avoid this difficultycrimped end portions of the Wires are preferably pressed against thesheet so that the wires rotate through about 90 and the undulations liein the main plane of the array. In a convenient method, illustrateddiagrammatically in FIG. 12 the supports 47 are placed on stands 91 oneither side of a glass sheet 92, the arrangement being such that thewires lie immediately above and in contact with the surface of theglass. Without the stands 91 the supports may tend to pull the wires andpartially uncrimp them. Weights 93 are laid on the crimped wires towardsbut not immediately adjacent to, opposite edges of the glass, so as topress the wires against the sheet and cause them to rotate as describedabove. The array of wires may then be secured in position by sprayingit, on either side of the weights 93, with a material which sets to forma thin transparent skin over the glass and wires. The Weights 93 arethen removed and those parts of the wires thus uncovered are secured byfurther spraying. When the array has been secured in position on theglass the surplus wire is cut off along the edges of the glass andremoved before the panel is completed.

When an array of crimped heating wires is incorp0- rated into alaminated transparent panel by this method it is found that some of thewires rotate one Way and some of the wires rotate the other way. Thisincreased randomness of the pattern made by the crimped wires in thecompleted panel reduces any tendency there may be for a reflective ordiffractive effect to be produced by light incident on the panel at anoblique angle.

The completed wired panel is illustrated in FIGS. 13 to 15. The panelcomprises two sheets of glass 92 and 94 with the array of wires 95secured against the sheet 92 as described above, and a sheet ofinterlayer material 96 between the array 95 and the sheet 94. Bus-barsor feed conductors 97 join the adjacent ends of the wires in the array,and the arrangement may be such that those parts of the wires beneaththe bus-bars are not crimped.

What we claim is:

1. A method of making a Wired panel in which an array of heating wiresis mounted on supporting edge members, and is crimped to formundulations which project from the main plane of the array, in which thearray of crimped wires is laid against one side of a sheet oftransparent material which is to form part of a laminated panel; crimpedend portions of the wires are pressed against said sheet, so that thewires rotate in random manner and the undulations lie in the main planeof the array, and the wires are secured to said sheet.

2. A method of manufacturing laminated transparent panels incorporatingan array of heating wires mounted on supporting edge members, comprisingthe steps of first crimping the wires forming the array so that eachwire is formed with undulations which project from the plane containingthe array and the supporting edge members, laying the array of crimpedwires against one side of a first sheet of transparent material which isto form part of a laminated panel, crimped end portions of the wiresthen being pressed against said first sheet so that the wires rotate inrandom manner and the undulations lie in the plane of the array, thensecuring the Wires to the first sheet prior to a second sheet formingthe other part of the laminated panel being joined to the first sheet.

References Cited UNITED STATES PATENTS 2,030,117 2/1936 Page 2l92032,813,960 11/1957 Egle et al. 219-445 3,378,919 4/1968 Brittan 29613 X3,392,759 7/1968 Davy et al. 29-61l X 3,418,448 12/1968 Pradenas 219213JOHN F. CAMPBELL, Primary Examiner V. A. DIPALMA, Assistant Examiner US.Cl. X.R. 2l9203

